field to be editable when the status is "Prepared' in Quote screen

Hi Team,

I have added a custom dropdown field to the Acumatica Quote (PM304500) screen. I want this field to be editable when the status is "Prepared," but it automatically becomes non-editable when the status changes. I have tried writing code in the Row_Selected event for the field to make it editable, but it's not working. Kindly provide me with a solution or let me know if there's a mistake I am making that is preventing it from working.

added this field in the  public class CRQuoteExt : PXCacheExtension<PX.Objects.CR.Standalone.CRQuote>

 #region UsrClosed
        [PXDBString(1)]
        [PXStringList(new string[] { "W", "L" },
                      new string[] { "Won", "Lost" })]
        [PXUIField(DisplayName = "Closed As")]
        public virtual string UsrClosed { get; set; }
        public abstract class usrClosed : PX.Data.BQL.BqlString.Field<usrClosed> { }
        #endregion

also added this field  public class PMQuoteExt : PXCacheExtension<PX.Objects.PM.PMQuote>
  { #region UsrClosed
        [PXDBString(1,BqlField=typeof(CRQuoteExt.usrClosed))]
        [PXStringList(new string[] { "W", "L" },
                      new string[] { "Won", "Lost" })]
        [PXUIField(DisplayName = "Closed As")]
        public virtual string UsrClosed { get; set; }
        public abstract class usrClosed : PX.Data.BQL.BqlString.Field<usrClosed> { }
        #endregion

added this code 

protected void PMQuote_RowSelected(PXCache cache, PXRowSelectedEventArgs e)
   {
     var row = (PMQuote)e.Row; 
     var rowExt = PXCache<PMQuote>.GetExtension<PMQuoteExt>(row);
       if (row.Status == "A")
                {
                 PXUIFieldAttribute.SetEnabled<PMQuoteExt.UsrClosed >(e.Cache, e.Row, true);

                }
   }